This invention relates to speech recognition and, more particularly, to a system capable of performing real time recognition of a large vocabulary by means of a signal processing card packaged on a bus of a personal computer (hereinafter called a PC).
Existing large vocabulary speech recognition systems are broadly divided into two categories according to their type of packaging.
A first category of speech recognition system performs speech recognition by storing in the recognition system all data on a vocabulary recognizable at a point of time, and by issuing the recognition result to a PC or the like (normally through a communication line such RS-232C). This system is often a box type (stand alone type) recognition system. Recognition systems of this type are very expensive because they require hardware for holding a large amount of data in the system. The DP-3000 speech recognition system of Nippon Electric Co., Ltd. is one speech recognition system of this type.
A second category of speech recognition system uses a signal processing card packaged on a bus of a PC for extracting characteristic values (alternatively, for extracting characteristic values and for labelling). The main processing for speech recognition is performed by a processor of the PC. Recognition systems of this type are inexpensive. However, a large part of the PC processor must be used for speech recognition itself, which often prevents the building of a large scale application using speech recognition or, on the other hand, may lead to a problem in the real time response speed of speech recognition. The Dragon Writer 1000 of Dragon Systems Inc. is one speech recognition system of this type.
No proposal has been known heretofore which realizes large vocabulary speech recognition at a low cost without imposing a load on the PC processor.